Performance
Core Web Vitals are three Google metrics that measure the real experience of visitors: LCP measures loading, INP measures responsiveness to clicks and taps, and CLS measures visual stability. A page does well when, at the 75th percentile of visits, LCP is 2.5 seconds or less, INP is 200 milliseconds or less and CLS is 0.1 or less. The guides below explain each metric, where the data comes from and how to fix what is slow.
Core Web Vitals: what LCP, INP and CLS are and how to improve them
What LCP, INP and CLS measure, the good and poor thresholds, how Google uses these metrics in Search and where to find your site's data.
Go deeper
- Performance
How to monitor performance across multiple sites and catch regressions
How an agency tracks Core Web Vitals across many sites: CrUX, its own RUM, scheduled tests, budgets, post-deploy alerts and client reports.
- Performance
Lighthouse, CrUX and RUM: which Core Web Vitals data to use
Lighthouse, CrUX and RUM measure different things. Where each comes from, the LCP, INP and CLS thresholds, and which to use to prioritize, debug and track.
- Performance
How to improve LCP: the four parts of LCP time
LCP breaks down into TTFB, resource load delay, load duration and render delay. How to measure each part and what to fix in each one.
- Performance
How to improve INP: what delays the response to a click
INP adds up input delay, processing and presentation. How to find the slow interaction and cut each phase, with scheduler.yield and LoAF.
- Performance
How to fix CLS: what makes the page jump
What counts in CLS, the common causes (images, ads, fonts, animations) and how to reserve space in HTML and CSS. How to find the element that moves.
Frequently asked questions
- Do Core Web Vitals affect rankings on Google?
- Google's ranking systems use these metrics, but a good result does not guarantee a position and does not outrank the relevance of the content, according to the Google Search Central documentation.
- Why is the Lighthouse score different from the Search Console data?
- Lighthouse simulates a single page load in the lab. Search Console shows CrUX field data, which gathers real visits from Chrome users over the last 28 days. The two measure different things and rarely match.
- Are mobile and desktop assessed together?
- No. Google assesses mobile and desktop separately, and a page can pass on one and not on the other.
- Are FCP and TTFB Core Web Vitals too?
- No. FCP and TTFB are supporting metrics, useful for diagnosis. The Core Web Vitals are only LCP, INP and CLS.
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